SubjectsPlus has an OAI component.
The code is located at:
There are 6 verbs
Identify, ListSets, ListRecords, ListMetadataFormats, GetRecord, ListRecords,records.
if you go to your subjectplus base url and then /oai/oai.php?verb=ListRecords you should see an xml file
However, you'll notice that puts out an error because there is a record that has single and double quotes which can't be processed by xsltprocessor v.1
Perhaps you can debug that.
If you view source on that page you should see the following: